The present invention relates to a monitor system and more particularly, to an image processing apparatus based on an image process for recognizing an object present inside a monitor area.
In a conventional video monitor apparatus, the inside of a monitor area was photographed at predetermined intervals with an image pickup unit such as a TV (television) camera and an acquired image is analyzed through image processing to recognize an object.
For example, in JP-A-2005-057743, an image obtained by photographing the inside of a monitor area is compared with a background image registered in advance to thereby recognize and detect an object and thereafter the detected object is pursued through a template matching method.
Also, in JP-A-2005-012548, with a view to decreasing the load imposed on an operation process as far as possible in a motion detection process, a general-use hardware engine for image reduction used for the purpose of generating an image for thumb nail display in, for example, a digital camera is utilized so that image data may be reduced and then an image process may be conducted.
In JP-A-2005-057743 mentioned as above, the background image and the input image are processed while keeping their sizes intact and so a slow processing speed results. More particularly, if a CPU (central processing unit) of low processing speed is used or if the number of pixels per frame is large and the number of pieces of data to be processed is large as in the case of, for example, a mega-pixel camera, the image processing cannot be carried out on real time base, thus leading to the possibility that missing of detection and erroneous detection will occur.
In case the number of pieces of data to be processed is decreased by reducing (thinning out) an image so as to relatively raise the processing speed, the image needs to be reduced simply. For example, when the distance from the camera is considered, an image picked up by the camera nears at the lower side of the screen and it goes away as it approaches the upper side of the screen. Accordingly, when considering the size of the object by the number of pixels, the object that exists in the position near from the camera has a larger pixels, and the same object that exists in the position far from the camera has a smaller pixels.
Since the image processing is executed in a unit of pixel (one pixel corresponding to one data piece), the result of processing becomes accurate as the number of pixels increases but the processing speed is low whereas the processing speed is fast as the number of pixels decreases but the accuracy of the processing result will be impaired. Especially, when many people come into the monitor area or a person coming thereinto is photographed in a large size, a decrease in the processing speed and a deterioration in the detection capability will result.
Accordingly, in order to execute the image processing accurately, the ratio of reduction of an image (reduction coefficient) needs to be changed appropriately in accordance with conditions of camera photography. In other words, in order for the image processing to be carried out constantly at appropriate reduction coefficients, the reduction coefficients need to be determined one by one by the user while changing the set value slightly and the reduction coefficient cannot be fixed. Therefore, an appropriate reduction coefficient must be computed in accordance with a monitoring location and a large processing amount is again generated.